1. Field
The present disclosure relates to high strength and aesthetic lithium disilicate crystalline glass-ceramics including cristobalite crystal and a preparation method thereof. The preparation method relates to a preparation of the high strength and aesthetic lithium disilicate crystalline glass-ceramics, dental restoration materials, and manufacturing methods which induce the growth of crystal phases or structures in a glass matrix with lithium disilicate crystal.
2. Discussion of the Background
With increased interest in appearance from economic development and increased income, the aesthetic aspect of prosthetic dental materials gains high attention. This leads to the introduction to different kinds of prosthetic restoration materials with aesthetic functions, and also to the development of various non-metal restoration materials.
Crown materials refer to prosthetic materials for restoration of the damaged teeth surfaces relevant to dentin and enamel. They are classified into inlay, onlay, veneer, and crown depending on the areas to be applied. Since they are applied to the outmost surfaces or teeth, not only aesthetic traits are highly required, but also high strength is demanded to endure chipping and/or wear against opposing dentition. Materials previously developed for crowns are leucite glass ceramics, reinforced porcelain, and fluorapatite (Ca5(PO4)3F) crystalline glass. Though they have high aesthetic traits, they are subject to fracture due to low flexural strength around 80 to 120 MPa. Therefore, various crown materials with high strength are being developed.
Lithium disilicate crystalline glass was introduced by Marcus P. Borom and Anna M. Turkalo (The Pacific Coast Regional Meeting, The American Ceramic Society, San Francisco, Calif., Oct. 31, 1973 (Glass division, No. 3-G-73P)) in 1973. They studied the formation of various crystal nuclei, and the different crystal phases and strength according to various heat treatment conditions for nuclei growth using glasses from Li2O—Al2O3—SiO2—Li2O—K2O—B2O3—P2O5. The high-temperature lithium disilicate crystal formed from low-temperature lithium meta-silicate showed its strength at 30-35 kps. It was due to the residual stress caused by the different thermal expansion coefficient of different phases, that is, reinforced glass, mother glass, Li2SiO5, and Li2SiO3 crystals.
High strength crystalline glass for dentistry (monolithic dental crown) using crystalline glass including lithium disilicate crystal has been provided. Although this crystalline glass has high aesthetic traits, the mechanical strength of monolithic crown manufactured by such method is low around 350 MPa, which is not adequate for posterior or bridges exposed to high stress. Therefore, various studies are under way to increase the strength of these aesthetic materials.